Thermal Analysis on Module Level in an Automotive Battery ... · Thermal Analysis on Module Level...

© FH AACHEN UNIVERSITY OF APPLIED SCIENCES | LES Lehrgebiet Energiespeichersysteme | COMSOL CONFERENCE 2016 MUNICH 13.10.2016 | 1

Thermal Analysis on Module Level in an Automotive Battery Package

Ziyi Wu M.Sc. 13.10.2016


Content


Motivation

Ground Model

Internal Cooling Fin

External Water Cooling

Summary


Motivation


Individual batteries have their own

operational temperature ranges

Many Li-Ion cells do not function

well above 60 °C

A good understanding of the

thermal behavior of the batteries

has its significance during designing

safe and robust battery packages

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800

100 °C

Capacity Retention (%)

Cycle Numbers

25 °C

60 °C

80 °C

0 200 400 600 800

-3

-2

-1

0

1

2

Time (s)

C-Rate

[Source: Linden‘s Handbook of Batteries] [Source: photo, ebaracus.com]

AHR18700M1Ultra graphite/LiFePO4

cell from A123 Systems


Ground Model - Battery Module


Z

X Y

Current Conductor

Cover

Case

Cell

Mandrel

- Pole

Gap between + Pole and active material

Spacer

+ Pole

48 V battery module with a least number of cells

15 identical cells High capacity power

cell from K2 Energy - K218650P01

[Source: K2 ENERGY]


SPECIFICATION

Nominal Capacity @ C/5 (Ah) 1.25

Average Operating Voltage @ C/5 (V) 3.2

Internal Impedance @ 1kHz, AC (mΩ) <19

RECOMMENDED OPERATING CONDITIONS

Continuous Discharge (A) 5.0

Charge Current (A) ≤1.25

High Operating Temp (°C) 60

Low Operating Temp (°C) -20

MAXIMUM OPERATING CONDITIONS

Continuous Discharge (A) 21

Charge Current (A) 2.4

High Operating Temp (°C) 85

Low Operating Temp (°C) -40

30

50

70

90

0 400 800 1200 1600 2000

-12.5

-7.5

-2.5

2.5

Time (s)

Current [A] SOC [%]

Ground Model - Load Profile


Load profile is derived from the technical data

Charging at 2 C-rate

Discharging at 8 C-rate

Cell Heating: 𝑄𝐶𝑒𝑙𝑙 = 𝐼2 ∙ 𝑅

Simulation duration: 20 ∙ 103 𝑠𝑒𝑐𝑜𝑛𝑑

[Source: K2 ENERGY]


0 4000 8000 12000 16000 20000

0

4

8

12

16

20

24

28

32

36

40

∆T (K)

Time (s)

Temperature - 𝑇𝑒𝑥𝑡 = 𝑇0 = 20 °𝐶

Convective Heat Flux - 𝑞0 = ℎ ∙ 𝑇𝑒𝑥𝑡 − 𝑇

Constant htc = 20 𝑊 (𝑚2 ∙ 𝐾)

Objective 1: 𝑇𝐶𝑒𝑙𝑙 ≤ 𝑇𝑟𝑒𝑐𝑜𝑚𝑚𝑒𝑛𝑑𝑒𝑑 𝑜𝑝𝑒𝑟𝑎𝑡𝑖𝑜𝑛

Objective 2: 𝑇𝐶𝑒𝑙𝑙_𝑀𝑎𝑥 − 𝑇𝐶𝑒𝑙𝑙𝑀𝑖𝑛≤ 3 𝐾

0 4000 8000 12000 16000 20000

0

2

4

6

8

10

12

14

16

18

∆T (K)

Time (s)

ICF_0

Temperature Gain of Hottest Cell

∆T between Hottest and Coldest Cell

Ground model – Results


316.3

320.7 330.6

322.4

332.6

323.6

XY-Cross Section ICF_0 @ 20000 s (K)


ICF_1 ICF_2 ICF_3 ICF_4 ICF_5 ICF_6

Internal Cooling Fin (ICF) Concepts

XY-Cross Section (mm2) 11.95 12.00 12.00 12.00 12.00 12.01

Circumference (mm) 12.25 25.13 16.00 19.00 26.00 23.50

Internal Cooling Fin - Concept


Temperature: 𝑇𝑒𝑥𝑡 = 𝑇0 = 20 °𝐶

Convective Heat Flux: 𝑞0 = ℎ ∙ (𝑇𝑒𝑥𝑡 − 𝑇)

Constant htc = 20 𝑊 (𝑚2∙𝐾)

Objective 1: 𝑇𝐶𝑒𝑙𝑙 ≤ 𝑇𝑟𝑒𝑐𝑜𝑚𝑚𝑒𝑛𝑑𝑒𝑑 𝑜𝑝𝑒𝑟𝑎𝑡𝑖𝑜𝑛

Objective 2: 𝑇𝐶𝑒𝑙𝑙_𝑀𝑎𝑥 − 𝑇𝐶𝑒𝑙𝑙_𝑀𝑖𝑛 < 3 𝐾

4 * Internal Cooling Fin


0 4000 8000 12000 16000 20000

0

4

8

12

16

20

24

28

32

36

40

∆T (K)

Time (s)

Internal Cooling Fin - Results


0 4000 8000 12000 16000 20000

0

2

4

6

8

10

12

14

16

18

∆T (K)

Time (s)



315.8

319.8 326.1

320.2

325.4

319.9

XY-Cross Section ICF_1_1 @ 20000 s (K)

ICF_0

ICF_1_1

ICF_3_1ICF_4_1ICF_5_1ICF_6_1

ICF_2_1




0 4000 8000 12000 16000 20000

0

4

8

12

16

20

24

28

32

36

40

∆T (K)

Time (s)

0 4000 8000 12000 16000 20000

0

2

4

6

8

10

12

14

16

18

∆T (K)

Time (s)

ICF_0

ICF_1_1


ICF_1_2

ICF_3_2

ICF_4_2ICF_5_2ICF_6_2

ICF_2_1



314.2

316.7 320.9

317.3

321.6

317.9



8 * Internal Cooling Fin


0 4000 8000 12000 16000 20000

0

4

8

12

16

20

24

28

32

36

40

∆T (K)

Time (s)


0 4000 8000 12000 16000 20000

0

2

4

6

8

10

12

14

16

18

∆T (K)

Time (s)




312.5

313.6 314.4

313.9

314.5

314.1


ICF_0

ICF_1_1


ICF_1_2

ICF_3_2

ICF_4_2ICF_5_2ICF_6_2

ICF_2_1

ICF_2_2




ICF & External Water Cooling

0 4000 8000 12000 16000 20000

0

1

2

3

∆T (K)

Time (s)

0 4000 8000 12000 16000 20000

0

2

4

6

8

10

12

14

16

18

20

22

24

∆T (K)

Time (s)



ICF_2_2

ICF_2_2-3


8 * ICF_2

Temperature -

𝑇𝑒𝑥𝑡 = 𝑇0 = 20 °𝐶

Velocity: 𝑈𝑊 = 1 𝑚 𝑠



ICF & External Water Cooling

0 4000 8000 12000 16000 20000

0

1

2

3

∆T (K)

Time (s)

0 4000 8000 12000 16000 20000

0

2

4

6

8

10

12

14

16

18

20

22

24

∆T (K)

Time (s)



ICF_2_2

ICF_2_2-3

ICF_2_2-5


8 * ICF_2

Temperature -

𝑇𝑒𝑥𝑡 = 𝑇0 = 20 °𝐶

Velocity: 𝑈𝑊 = 1 𝑚 𝑠



Summary

Simulative thermal analysis contributes in gaining knowledge of the cell heating during

operational conditions

a helpful step before conducting actual tests

The simulation results show, the temperature distribution in the ground model of the battery

module is greatly uneven

differences in cell cycle life within the same battery module

a shortened cycle life of the entire module

Cooling systems for the battery module shall be considered as an indispensable component in

battery systems for automotive applications

Combine systems with different cooling principle shall be involved for large battery module

a homogenous temperature distribution

ensure the function of all cells


Thank you!Thank you!

FH Aachen University of Applied SciencesFaculty of Aerospace Engineering - Energy Storage Systems

Ziyi Wu M.Sc.Hohenstaufenallee 652064 Aachen | Germany

T +49.241.6009 52880F +49.241.6009 [email protected]

Prof. Dipl.-Ing. Hans KemperHohenstaufenallee 652064 Aachen | Germany

T +49.241.6009 52485F +49.241.6009 [email protected]

Thermal Analysis on Module Level in an Automotive Battery ... · Thermal Analysis on Module Level...

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